Author Topic: SNK Games (Neo Geo MVS/AES) (Read 130620 times)

channelmaniac · « **Reply #120 on:** May 23, 2014, 09:16:54 PM »

Model: MV4
Symptom: Very low audio. Missing audio on slot 4

Recapped audio section to fix low audio issues. Replaced a bad 74LS244 on the top board to fix the missing audio on slot 4. Installed a new battery per owner's request.

channelmaniac · « **Reply #121 on:** May 23, 2014, 09:17:06 PM »

Model: MV6
Symptom: Slot 1 not working

Repaired 3 burned traces on the top board and tested. It appears the board was powered up wet since the traces that were burned were once that are grounded and next to the power pin on 3 of the 74LS244 ICs.

channelmaniac · « **Reply #122 on:** May 23, 2014, 09:17:19 PM »

Model: MV4FT2
Symptom: Graphic corruption, battery corrosion damage

Re-mounted the battery to the top side of the bottom board, jumpered 3 corroded traces on the bottom board, sealed up 8 scraped traces on the bottom of the bottom board, then cleaned the top board & slots. Removed a bent pin from slot 2, fixed the bad soldering on a user installed RCA jack connecting a pause button, and replaced 2 missing screws. Tested board.

channelmaniac · « **Reply #123 on:** May 23, 2014, 09:17:51 PM »

Model: MV4FT2
Tip: Battery corrosion damage

When the battery leaks on the MV4FT2 version of the Neo Geo 4 slot, there are 3 traces that run next to the battery area that control the graphics on the slots that can be affected by the corrosion damage. If this happens, the graphics will come and go, especially when touching pin 56 of the NEO-253 chip at D5 on the top board with a logic probe or oscilloscope probe.

The trace from this pin routes to the bottom board and is one of the three traces that run next to the battery area on the top side of the bottom board. These three traces will most likely be damaged and require jumpering with 30ga Kynar wire.

channelmaniac · « **Reply #124 on:** May 23, 2014, 09:17:59 PM »

Model: MV2
Symptom: Graphic corruption

Board had rodent damage on one of the NEO-257 ICs. Cleaned the board and slots then replaced a leaking battery. Tested.

channelmaniac · « **Reply #125 on:** May 23, 2014, 09:18:17 PM »

Model: MV2F
Symptoms: Vertical lines on both slots

Board had a leaking battery. Cleaned up the battery corrosion and jumpered 2 traces between the NEO-257 and the NEO-ZMC2 ICs to fix slot 1. Jumpered a bad trace between slot 2 and the NEO-257 IC to fix slot 2. Installed a new battery and tested.

channelmaniac · « **Reply #126 on:** May 23, 2014, 09:18:26 PM »

Model: MV4
Symptom: Low audio, replace battery

Customer requested battery change. Installed cap kit and battery. Tested.

channelmaniac · « **Reply #127 on:** May 23, 2014, 09:18:33 PM »

Model: MV2F
Symptom: Low audio on one channel and lines on screen

Battery was leaking. Removed battery, cleaned board, and installed cap kit to fix audio issue. Replaced bad NEO-257 IC to fix lines on screen. Installed new battery and tested.

channelmaniac · « **Reply #128 on:** May 23, 2014, 09:18:43 PM »

Model: MV1
Symptom: Backup RAM Error

Board had a Backup RAM Error at D0000, Written 0000, Read 04D0. Replaced bad 74HC32 chip controlling the enable lines. Board then gave a Backup RAM error at D0008. Replaced one 62256 SRAM chip and tested. Board had no audio. Replaced 2 physically broken 470uf @ 16v caps to finish the repair.

channelmaniac · « **Reply #129 on:** May 23, 2014, 09:18:58 PM »

Model: MV4
Symptom: Work RAM Error

Replaced bad SRAM at location G9 and ran self tests. Audio level was low. Installed audio cap kit and tested. Board would not read any carts. Replaced a corroded 74LS244 on the top board, cleaned the rodent damage, and patched 2 traces. Tested.

channelmaniac · « **Reply #130 on:** May 23, 2014, 09:19:12 PM »

Model: MV1
Symptom: Work RAM Error: Written AAAA Read: AA2A

Replaced the SRAM at location H3 and tested.

channelmaniac · « **Reply #131 on:** May 23, 2014, 09:19:20 PM »

Model: MV6
Symptom: No Audio

Board had very faint audio when running hardware test. Recapped board and tested. Board had strong audio in test mode but no audio for games. Reset backup RAM and tested. Corrupt backup RAM was causing the audio to not work.

channelmaniac · « **Reply #132 on:** May 23, 2014, 09:19:29 PM »

Model: MV4
Symptom: Very low audio

Installed audio cap kit and tested.

channelmaniac · « **Reply #133 on:** May 23, 2014, 09:19:37 PM »

Model: MV4
Symptom: Low Audio

Installed Cap Kit and tested.

channelmaniac · « **Reply #134 on:** May 23, 2014, 09:19:45 PM »

Model: MV4
Symptom: Low Audio

Board would not play hardware test tones. Game audio worked, but was low. Installed cap kit to fix audio levels. Replaced bad SM1 ROM to fix the hardware test tones.

channelmaniac · « **Reply #135 on:** May 23, 2014, 09:19:53 PM »

Model: MV4
Symptom: Crosshatch of death

Removed leaking battery and cleaned board. Repaired 12 bad traces and tested.

channelmaniac · « **Reply #136 on:** May 23, 2014, 09:20:02 PM »

Model: MV1
Symptom: Tinny sounding audio

Cleaned the stereo/mono switch and replaced a bad battery that had started to leak. Tested.

channelmaniac · « **Reply #137 on:** May 23, 2014, 09:20:12 PM »

Model: MV1
Symptom: Stuck on Green

Board had the battery already removed and had minimal corrosion damage but still had the crystal and D4990 clock chip with some on it. Cleaned the corrosion, including some bridging the crystal's leads and tested the board. The corrosion bridge caused the crystal to not oscillate. Replaced the missing battery and tested.

channelmaniac · « **Reply #138 on:** May 23, 2014, 09:20:23 PM »

Model: MV1
Symptom: Z80 Error

Board was labeled Z80 error but had multiple issues caused by battery leakage, attempted repairs, and rodent damage. Removed an extra Z80 CPU from the BIOS socket and installed the correct BIOS chip. Removed leaking battery, cleaned board, and replaced crystal to fix calendar error. Patched a bad trace going to the cartridge port. Z80 Error had 2 causes. The first was a corroded trace between the NE0-D0 chip, pin 40 and NE0-B0 pin 41. The Z80 Error returned during testing and the IRQ pins on the CPU had bad signals. Pins 36 and 37 on the NE0-D0 read 50 ohms between them. This drove the NMI and IRQ lines for the Z80 CPU. Removed the NE0-D0 IC, cleaned the rodent damage under it, and reinstalled it and the patch to the B0 chip. Tested.

The rodent damage corroded the solder on the plated thru holes under the NE0-D0 IC. This corrosion was bridging the 2 pads causing the problems.

channelmaniac · « **Reply #139 on:** May 23, 2014, 09:21:29 PM »

Model: MV4
Symptom: Constantly reboots with Calendar Error

System was odd in that it would come up with a Calendar Error message then reboot. The reboot was odd since the system should've stayed on the Calendar Error screen. Disassembled system only to find that it worked fine. Tapping the board caused the problem to intermittently return. Resoldered bad connections on the surface mount Work and Backup RAM to fix.

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Author Topic: SNK Games (Neo Geo MVS/AES) (Read 130620 times)